Dendrites - this is what? The structure and functions of dendrides

The neural tissue, consisting of neurons and neuroglia, performs a complex of the most complex and responsible functions: it produces weak electrical impulses, which are then transmitted to the muscles and organs of man or vertebrate animals. The cells of this tissue have a special structure. It ensures both the emergence of excitation and inhibition processes, and their conduct. In neuroscience, there is a definition: dendrites are the processes of the nerve cell that perceive and transmit information to the neuron's body. In this paper, we will get acquainted with modern ideas about the mechanisms of nerve impulse transmission in the main parts of the nervous system: the brain and spinal cord, and also study the structure of dendrites as one of the constituent parts of neurocytes.

To do this, we consider in more detail the features of the structure of a neuron, which is an elementary unit of the nervous tissue.

How the structure of the neurocyte is related to its functions

Electron microscopic research methods confirmed the fact of high specialization and complex device of an open biological system, called a nerve cell. It contains a body (soma), one long branch - an axon and a set of short processes. Each of them is connected to the cytoplasm of the body of the neuron. It's a dendrite. The structure and appearance of the aggregate of short processes resembles the crown of a tree. On them to the body of the neuron through the synapses bioelectric potentials from other nerve cells arrive.

Morphology and types

According to modern histology studies, dendrites are branching neuronal endings, not only receiving but also transmitting information encoded in the form of electrical impulses, along a multichannel system of anatomically and functionally interconnected nerve cells. They contain a large number of protein-synthesizing organelles - ribosomes. Some kinds of short processes, for example in pyramidal neurocytes, are covered with special structures - spines.

According to the classification proposed by the Spanish neurohistologist S. Ramon-i-Cahal, two dendrites can move away from the body of the nerve cell in opposite directions (bipolar neurocytes). If there are many dendrites, then they diverge radically from the soma. This structure is characteristic of interneurons. In the cerebellar cages of Purkinje, the processes come out of the body of the neurocyte in the form of a fan. Each dendrite, whose structure is three-dimensional, differs from neighboring branches by the amount of electric charges accumulated on it.

What affects the branching of the nerve processes

The body of a neuron is a universal transmitting and simultaneously accepting biological object. The volume (primarily incoming information) is directly proportional to the number of incoming nerve impulses. They are determined by the degree of branching of the dendritic tree. Therefore, dendrites are structures of the neurocyte that play an integrative function.

Moreover, the processes expand the area of contact of the nerve cells with each other. Additional synaptic formation at times increases the efficiency of all departments, such as the brain and spinal cord, and the nervous system as a whole.

The structure of the dendrite

Based on the study of microscopic preparations of nerve cells, it was established that most of the processes have a cylindrical shape. Their average diameter is 0.9 μm. The length of the dendrites varies widely. For example, stellate neurons of the gray matter of the cerebral cortex have short (no more than 200 μm) branches of the dendritic tree, whereas the processes of the motor neuron entering the anterior horns of the spinal cord are of the order of 2 mm.

Special formations - spinules formed on the branches of neurocytes, lead to the appearance of a large number of synapses - sliced places of contact with the axon, dendritic or soma of another neuron. Synapses can be located on the body of the dendrite and are called stem cells or directly on its spines. As we already know, dendrites are branched processes of neurocytes, capable of receiving excitement. Transmission of the same biopotentials occurs in them with the help of molecules of chemical compounds - mediators, for example, GABA or acetylcholine. In the membrane covering the dendrite, ion channels that selectively pass the cations of calcium, sodium and potassium involved in the passage of nerve impulses through the neuron are found.

How information enters the nerve cell

In the process of transfer of electric charges, underlying the excitation and inhibition, along with the axon, dendrites also participate. These are the processes of the neuron, which form synapses with branches of the dendritic tree of other neurocytes. It was established experimentally that the dendrites are the outgrowths of the cell cytoplasm covered with a membrane. It produces weak electrical impulses - the action potentials.

Thanks to the system of short processes, one nerve cell perceives and transmits several thousand such pulses, generated by synapses. This is not the only function of dendrites. They also process and integrate information entering the neurons, which ensures the regulation and control exercised by the nervous system over all organs and tissues of the human body.